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Compound subretinal prostheses with extra-ocular parts and surgical technique thereforeRelated Patent Categories: Surgery: Light, Thermal, And Electrical Application, Light, Thermal, And Electrical Application, Electrical Therapeutic Systems, Producing Visual Effects By StimulationCompound subretinal prostheses with extra-ocular parts and surgical technique therefore description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070250135, Compound subretinal prostheses with extra-ocular parts and surgical technique therefore. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] For degenerative retinal diseases such as retinitis pigmentosa (RP) retinal prostheses represent one major potential treatment. With increasing numbers of human trials being performed retinal prostheses seem to be the nearest treatment option for patients suffering from these diseases at present; see e.g. U.S. Pat. No. 6,761,724 to Zrenner et al., and U.S. Pat. No. 5,024,223 to Chow. [0002] Since 1995 there has been collected promising evidence of the feasibility of a subretinal prosthesis based on a microphotodiode array (MPDAs) which stimulates the retina from the subretinal space by transforming light energy into electrical energy. Evidence for the possibility to elicit spatially ordered responses in the cortex of animals is numerous and solid; see e.g. Eckhorn, et al. (2001), Physiological functional evaluation of retinal implants in animal models, Opthalmologe 4:369-375; Gekeler et al. (2004), Subretinal electrical stimulation of the rabbit retina with acutely implanted electrode arrays, Graefes Arch Clin Exp Opthalmol 7:587-596; and Schanze et al. (2005), Implantation and testing of subretinal film electrodes in domestic pigs, Exp Eye Res 82(2):332-40. [0003] Questions concerning biocompatibility and biostability seem to a large extent be solved. There has also been presented evidence for the necessity to introduce extra energy in addition to the energy which subretinal photodiodes are capable to produce solely from transforming the light falling onto them into electrical energy; see e.g. Stett et al. (2000), Electrical multisite stimulation of the isolated chicken retina, Vision Res 40:1785-1795; and Stett et al. (1998), Electrical stimulation of degenerated retina of RCS rats by distally applied spatial voltage patterns, Invest Opthalmol Vis Sci Abstract Annual Meeting. [0004] This is in contradiction to other groups who believe subretinal implants consisting of MPDAs without external energy will produce enough electrical energy to stimulate the visual system; see Chow et al. (2004), The artificial silicon retina microchip for the treatment of vision loss from retinitis pigmentosa, Arch Opthalmol 4:460-469. [0005] Therefore, for the prosthesis of this application extra energy is crucial and currently two main different approaches are being investigated for introduction of this energy into the implant system: energy from infrared irradiation sources, as disclosed in U.S. Pat. No. 6,298,270, or energy transferred via high-frequency coils, as disclosed in U.S. Pat. No. 6,847,947. [0006] While these forms are wireless they are not yet readily available for human. Therefore, at present it is unavoidable to use subretinal prostheses with permanent extra-ocular connections to supply required additional energy. Humayun et al. (2003), Visual perception in a blind subject with a chronic microelectronic retinal prosthesis, Vision Res 24:2573-2581, report to have implanted epiretinal prosthesis with extra-ocular parts permanently into human volunteers. While the implant and the surgical procedure appear similar to the subretinal approach, several distinct differences exist: the subretinal implant used in this application and designed for human trials contained a much higher number of electrodes to elicit useful resolution (1550 vs. 16) and thus required a higher amount of additional energy; and epiretinal implantation techniques are easier from the viewpoint of the intraocular surgical procedure itself because they usually do not require extensive retinal surgery. To implant a compound system into the subretinal space and place external connections from there is the current challenge before human trials with this kind of prosthesis can be performed. [0007] All previous studies with subretinal implants have only partially addressed and solved the surgical and technical problems arising from subretinal implantation of compound devices. They have been insufficient in not providing proof of the feasibility of the implantation of compound systems--from subretinal microphotodiodes to polyimide foils for choroidal access and silicone cables for transcutaneous energy supply; in addition, most of these experiments only acutely stimulated the visual pathways; see e.g. Sachs et al. (2005), Transscleral implantation and neurophysiological testing of subretinal polyimide film electrodes in the domestic pig in visual prosthesis development, J Neural Eng 1:S57-S64; and Schanze et al. (2005), Implantation and testing of subretinal film electrodes in domestic pigs, Exp Eye Res 82(2):332-40. SUMMARY OF THE INVENTION [0008] In view of the above, the object underlying the present invention is to improve the known subretinal implants and the surgical technique for introducing same into the subretinal region. [0009] The study underlying the present application has been proven the feasibility of long-term implantation of a new subretinal device which closely resembles the device for first human trials. [0010] According to one object of the present invention, the implant is designed to allow stable fixation on the sclera as well as on the skull; it is a compound system containing all parts necessary for long-term stimulation. [0011] According to another object, it carries on its tip two different functional entities. First, an active MPDA of 1550 microphotodiodes, amplifiers, and electrodes (dimensions 3.times.3.times.0.1 mm; array grid 70 .mu.m). It works autonomously and stimulates neighbouring neuroretinal tissue depending on relative light intensities. Second, a 4.times.4 array of electrodes spaced 280 .mu.m that can be addressed externally for direct stimulation (DS) of neuroretinal tissue. Charge injection delivered by each DS electrode can be controlled by a wireless stimulator, modulating amplitude, waveform, duration, frequency, and interstimulus intervals and allows highly controlled electrical stimulation in order define optimal pulses for subretinal electrical stimulation. [0012] According to a further object of the invention, surgical implantation technique has been altered in such a way that it now minimizes damage to the retina and the retinal pigment epithelium (RPE) and allows highly controlled introduction into the subretinal space to the exact required position. The feasibility of the approach has been proven by clinical examination (opthalmoscopy, biomicroscopy), fluorescein angiography (FA), optical coherence tomography (OCT), and histology. Behavioural examination has demonstrated clear changes in animal behaviour following subretinal electrical stimulation. [0013] The inventors succeeded in successful long-term implantation of a compound subretinal prosthesis with extra-ocular parts and energy coupling which represents the final step towards shortly forthcoming human trials. [0014] The implant consisted of a microphotodiode array (MPDA) with 1.550 electrodes and a 4 by 4-array of gold electrodes for direct electrical stimulation; both were mounted onto a polyimide foil for transscleral placement into the subretinal space. The foil carried connection lanes to a silicone cable which was implanted under the skin and lead to a stimulator box in the animal's neck. Surgery was performed in eleven domestic pigs. [0015] The new vitreo-retinal surgical technique comprises a 180.degree. peripheral retinotomy and preferably use of diathermia to penetrate the choroid in order to avoid choroidal hemorrhage. This is contrary to the disclosure of U.S. Pat. No. 6,761,724, that teaches a direct, transscleral, transchoroidal access to the subretinal region without opening the intraocular region to avoid operation risks of vitrectomy and retinotomy. [0016] Subretinal forceps are used to place the implant safely onto the retinal pigment epithelium before the retina is flattened. Preferably, peripheral laser photocoagulation is applied and the eye is filled with silicon oil. [0017] According to one object, the implant is stabilized by a scleral fixation patch, and further preferably by use of a metal clamp with bone screws on the animal's skull and a tissue ring under the animal's skin in the neck. [0018] All implants were successfully placed subretinally. In 3 animals a proliferative vitreo-retinopathy was observed after approximately 2 weeks. Otherwise, funduscopy and OCT demonstrated complete retinal attachment and FA showed no retinal vascular abnormalities over and around the implant. The animals showed clear behavioural reactions to electrical stimulation over the whole examination period. Histological examination failed to show any voltage-induced alteration in the cellular architecture of the retina overlying the stimulation electrodes. [0019] This demonstrates the feasibility of the new surgical procedure for highly safe and controlled implantation of complex subretinal devices with extra-ocular parts. BRIEF DESCRIPTION OF THE DRAWINGS [0020] FIG. 1 [0021] Compound subretinal implant with microphotodiode array (MPDA) and 16 subretinal electrodes for direct stimulation (DS). Continue reading about Compound subretinal prostheses with extra-ocular parts and surgical technique therefore... 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